An amperometric sensor employing glucose oxidase immobilized on nylon membranes with different pore diameter and grafted with different monomers

Glucoseoxidase (GOD) was immobilized on nylonmembranes having three differentporediameters and chemically grafted with glycidyl methacrylate (GMA) or butyl methacrylate (BMA). Hexamethylenediamine (HMDA) and glutaraldehyde (GA) were used as spacer and coupling agent, respectively. The biochemical and electrochemical behaviour of the membranes has been studied as a function of pH, temperature and glucose concentration with reference to the graftedmonomer and the membraneporediameter. The behaviour of the soluble GOD has also been studied in order to see the modification induced by the immobilization process on the enzyme activity. It was found that the values of the biosensor sensitivity, maximum saturation current and electrochemical affinity increase with the membraneporediameter, indipendently of the nature of the graft monomer. Opposite behaviour was found relatively to the extension of the linear response ranges and the average response times. With reference to the parameters increasing with the porediameter it was found that membranesgrafted with GMA had higher values than those of the membranesgrafted with BMA. The contrary occurred to the values of the parameters decreasing with the increase of the porediameter. Biochemical and electrochemical results have been discussed in terms of the different limitations to the diffusion of substrate and reaction products across the catalytic membrane introduced by the differentporediameters and by the different hydrophobicity of the graft monomers.